U.S. patent application number 17/409893 was filed with the patent office on 2022-03-17 for sustainable calcium hydroxide production for green cement.
The applicant listed for this patent is WISCONSIN ALUMNI RESEARCH FOUNDATION. Invention is credited to Robert Phillip Anex, Raghavendra Ragipani, Thatcher Wiley Root, Bu Wang.
Application Number | 20220081311 17/409893 |
Document ID | / |
Family ID | |
Filed Date | 2022-03-17 |
United States Patent
Application |
20220081311 |
Kind Code |
A1 |
Wang; Bu ; et al. |
March 17, 2022 |
SUSTAINABLE CALCIUM HYDROXIDE PRODUCTION FOR GREEN CEMENT
Abstract
A method of making a composition of matter comprising calcium
hydroxide. The method includes the steps of contacting a
calcium-containing molecule with an aqueous solution of a
water-soluble salt having ammonium cation and a counter-anion,
under conditions effective to yield a compound containing calcium
and the counter-anion; and reacting the compound comprising calcium
and the counter-anion with ammonia and water under conditions to
yield calcium hydroxide.
Inventors: |
Wang; Bu; (Madison, WI)
; Ragipani; Raghavendra; (Madison, WI) ; Anex;
Robert Phillip; (Madison, WI) ; Root; Thatcher
Wiley; (Madison, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WISCONSIN ALUMNI RESEARCH FOUNDATION |
Madison |
WI |
US |
|
|
Appl. No.: |
17/409893 |
Filed: |
August 24, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63069936 |
Aug 25, 2020 |
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International
Class: |
C01F 11/12 20060101
C01F011/12; C04B 7/42 20060101 C04B007/42 |
Goverment Interests
FEDERAL FUNDING STATEMENT
[0002] This invention was made with government support under
DE-FE0031705 awarded by the US Department of Energy. The government
has certain rights in the invention.
Claims
1. A method of making a composition of matter comprising calcium
hydroxide, the method comprising: (a) contacting a material
comprising calcium-containing molecules with an aqueous solution
comprising a water-soluble salt comprising ammonium cation and a
counter-anion, for a time, and at a temperature, pH, and pressure
effective to yield a compound comprising calcium and the
counter-anion; and (b) reacting at least a portion of the compound
comprising calcium and the counter-anion with ammonia and water for
a time, and at a temperature, pH, and pressure effective to yield
calcium hydroxide.
2. The method of claim 1, wherein the water-soluble salt comprising
ammonium cation and a counter-anion is selected from the group
consisting of ammonium halide, ammonium acetate, ammonium
phosphate, ammonium oxalate, and ammonium lactate.
3. The method of claim 1, wherein the water-soluble salt comprising
ammonium cation and a counter-anion is ammonium chloride or
ammonium acetate.
4. The method of claim 1, wherein step (b) yields calcium hydroxide
and ammonium halide and further comprising: (c) recycling at least
a portion of the ammonium halide formed in step (b) and using it as
the water-soluble salt comprising ammonium cation and a
counter-anion.
5. A method of making a composition of matter comprising calcium
hydroxide, the method comprising: (a) contacting a material
comprising calcium-containing molecules with an aqueous solution
comprising a water-soluble salt comprising ammonium cation and a
counter-anion, for a time, and at a temperature, pH, and pressure
effective to yield a compound comprising calcium and the
counter-anion; (b) reacting at least a portion of the compound
comprising calcium and the counter-anion with ammonia and water for
a time, and at a temperature, pH, and pressure effective to yield
calcium hydroxide; and (c) recycling at least a portion of the
ammonium halide formed in step (b) and using it as the
water-soluble salt comprising ammonium cation and a
counter-anion.
6. The method of claim 5, wherein the water-soluble salt comprising
ammonium cation and a counter-anion is selected from the group
consisting of ammonium halide, ammonium acetate, ammonium
phosphate, ammonium oxalate, and ammonium lactate.
7. The method of claim 5, wherein the water-soluble salt comprising
ammonium cation and a counter-anion is ammonium chloride or
ammonium acetate.
8. A method of making a composition of matter comprising calcium
hydroxide, the method comprising: (a) contacting a material
comprising calcium-containing molecules with an aqueous solution
comprising ammonium chloride, for a time, and at a temperature, pH,
and pressure effective to yield a compound comprising calcium
chloride; and (b) reacting at least a portion of the calcium
chloride of step (a) with ammonia and water for a time, and at a
temperature, pH, and pressure effective to yield calcium hydroxide
and ammonium chloride.
9. The method of claim 8, further comprising: (c) recycling at
least a portion of the ammonium chloride formed in step (b) and
using it as the ammonium chloride in step (a).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Priority is hereby claimed to provisional application Ser.
No. 63/069,936, filed Aug. 25, 2020, which is incorporated herein
by reference.
BACKGROUND
[0003] Globally, cement production is responsible for the release
of about 3 billion tons of carbon dioxide (CO.sub.2) per year,
which is approximately 8% of total global CO.sub.2 emissions.
Production has increased more than thirty-fold (30.times.) since
1950 and almost four-fold (4.times.) since 1990. In the future,
cement is expected to play a vital role in the expansion of the
built environment, especially in emerging economies. Forecasts of
global cement production in 2050 range from 3.7 to 5.5 billion tons
annually. If produced using current methods, the emissions
associated with the production of that amount of cement alone would
account for as much as 40% of the world's carbon budget in 2050.
(By "carbon budget" is meant the emissions allowable for a 50%
chance of limiting the rise in average global temperature to
1.5.degree. C. in 2050).
[0004] The barriers to the decarbonization of the cement industry
are well known. More than half (about 55%) of cement-sector
CO.sub.2 emissions result from the thermal decomposition of
limestone (CaCO.sub.3) to form CaO and CO.sub.2. Another roughly
40% comes from burning fossil fuels to provide the heat to drive
this process. The remaining CO.sub.2 balance is generated from the
energy used to grind and transport the limestone and other
materials. From 2014 to 2017, the direct CO.sub.2 intensity of
cement production increased by 0.3% per year.
[0005] Cement plants are large, expensive, and have long lifespans.
As a result, the cement sector is essentially an oligopoly; it is
dominated by a small number of major producers who are reluctant to
change business models or experiment with new technology. Overall,
when cement emissions are mentioned at all in public debate, it is
typically to note that little can be done about them.
[0006] U.S. Pat. No. 10,369,518, issued Aug. 6, 2019, to Tate et
al., describes a method of forming a composition of mater that
comprises calcium hydroxide. The method generally includes the
steps of combining particles of calcium oxide (CaO) and water to
form calcium hydroxide (Ca(OH).sub.2) particles; milling the
calcium hydroxide particles to reduce the particle size diameter of
the calcium hydroxide particles; and then drying the calcium
hydroxide particles. The resulting composition of matter has a D10
particle size distribution of from about 0.5 to about 4
micrometers, a D90 less than about 30 micrometers, a ratio of D90
to D10 of from about 8 to about 20, and a flow factor index from
about 2 to about 4. The individual calcium hydroxide particles
include a surface area greater than or equal to about 25
m.sup.2/g.
[0007] U.S. Pat. No. 10,266,451, issued Apr. 23, 2019, to Hempel et
al., describes a method to make a building material based on
calcium hydroxide. The method includes the steps of mixing hemp
shavings with lime to produce a structural mass. Water is then
added in a sufficient amount to yield a paste that can be worked.
Then at least one powder based on natural materials of volcanic
origin, such as pozzalana, is added to the structural mass.
[0008] There remains a long-standing, acutely desired, and unmet
need for a more sustainable method to manufacture cement--a method
that does not generate such a large volume of CO.sub.2.
SUMMARY
[0009] To address this long-felt, unmet need, described herein is a
novel, sustainable process to manufacture the material that is most
critical to cementation--calcium hydroxide (Ca(OH).sub.2). This new
process utilizes a low-temperature ammonia cycle to produce calcium
hydroxide from a wide range of calcium-bearing industrial waste
streams such as recycled concrete and coal ashes.
[0010] Thus, disclosed herein is a method of making a composition
of matter comprising calcium hydroxide. The method includes the
step contacting a material comprising calcium-containing molecules
with an aqueous solution comprising a water-soluble salt comprising
ammonium cation and a counter-anion, for a time, and at a
temperature, pH, and pressure effective to yield a compound
comprising calcium and the counter-anion. Because of the presence
of the ammonium salt, the pH of the reaction solution will
generally be neutral to alkaline, i.e., equal to or greater than 7.
The reaction is preferably carried out at room temperature (roughly
15 to 20.degree. C.), but elevated temperatures up to the boiling
point of the reaction solution at atmospheric pressure may be used.
The reaction is preferably carried out at atmospheric pressure,
although elevated pressures up to about 10 bar may be used.
[0011] Supernatant from the first step is rich in dissolved
calcium. Supernatant from the first step is reacted is reacted with
ammonia and water for a time, and at a temperature, pH, and
pressure effective to yield calcium hydroxide, which precipitates
from the reaction solution. This second step is preferably carried
out at elevated temperatures, from about 30.degree. C. to about
100.degree. C. or from about 50.degree. C. to about 75.degree.
C.
[0012] It is preferred that the water-soluble salt comprising
ammonium cation and a counter-anion is halide or weak acid anions
including phosphate acetate, oxalate, and lactate, most preferably
ammonium chloride or ammonium acetate.
[0013] If ammonium chloride is used in the first step, the second
step regenerates the ammonium chloride. The ammonium chloride so
formed may optionally be recycled and used again in the first step.
The same recycling strategy may be applied to other ammonium
halides, and to the other water-soluble ammonium salts
mentioned.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a stylized schematic diagram showing the overall
method disclosed herein.
[0015] FIG. 2 shows the chemical reactions for the mineral
dissolution and hydrolysis steps described here, along with the
overall combination of the two reactions (which yields Ca.sup.2+
ions). Lastly is shown the ammonium absorption and precipitation
reactions, in which the Ca.sup.2+ ions are reacted with Cl.sup.-,
NH.sub.4.sup.+, and OH.sup.- ions to yield Ca(OH.sub.2), which
precipitates from solution.
[0016] FIG. 3 is a formal schematic diagram showing an exemplary
apparatus that can be used to practice the method disclosed and
claimed herein.
DETAILED DESCRIPTION
[0017] Numerical ranges as used herein are intended to include
every number and subset of numbers contained within that range,
whether specifically disclosed or not. Further, these numerical
ranges should be construed as providing support for a claim
directed to any number or subset of numbers in that range. For
example, a disclosure of from 1 to 10 should be construed as
supporting a range of from 2 to 8, from 3 to 7, from 1 to 9, from
3.6 to 4.6, from 3.5 to 9.9, and so forth.
[0018] All references to singular characteristics or limitations of
the present invention shall include the corresponding plural
characteristic or limitation, and vice-versa, unless otherwise
specified or clearly implied to the contrary by the context in
which the reference is made. The indefinite articles "a" and "an"
mean one or more.
[0019] All combinations of method or process steps as used herein
can be performed in any order, unless otherwise specified or
clearly implied to the contrary by the context in which the
referenced combination is made.
[0020] The method disclosed herein can comprise, consist of, or
consist essentially of the essential elements and limitations of
the method described herein, as well as any additional or optional
steps or limitations described herein or otherwise useful in
chemical engineering.
[0021] The term "contacting" refers to the act of touching, making
contact, or of bringing to immediate or close proximity, including
at the molecular level, for example, to bring about a chemical
reaction, or a physical change, e.g., in a solution or in a
reaction mixture.
[0022] An "effective amount" refers to an amount of a chemical or
reagent effective to facilitate a chemical reaction between two or
more reaction components, and/or to bring about a recited effect.
Thus, an "effective amount" generally means an amount that provides
the desired effect.
[0023] Referring now to FIG. 1, the figure is a stylized schematic
diagram of the novel method to make calcium hydroxide
(Ca(OH).sub.2) as disclosed and claimed herein. Ca(OH).sub.2 is a
critical ingredient in cement. (Ca(OH).sub.2 is also referred to as
"slaked lime.") It plays a central role in the hydration reactions
that drive the curing of wet cements and concretes comprising the
cements. It also plays a role in the final physical-mechanical
characteristics of the cured cement/concrete.
[0024] As shown in FIG. 1, the raw material for the present method
is calcium-containing waste streams, such as recycled concrete,
bottom ash, fly ash, and the like. Typically, these materials are
landfilled or stored in large "ash ponds." An "ash pond," also
called a coal ash basin or surface impoundment, is an engineered
storage structure used at fossil fuel power stations to hold bottom
ash and fly ash. ("Bottom ash" is part of the non-combustible
residue of combustion in coal-fired power plants, boilers,
furnaces, and incinerators. Bottom ash is the heavier,
non-combustible ash ("clinkers") that form inside the combustion
chamber and fall to the bottom of the chamber due to gravity. The
lighter portion of the ash that escapes up the chimney is "fly
ash." In modern, coal-burning facilities, the lion's share of the
fly ash is isolated using scrubbers and impounded in an ash pond
along with the bottom ash. The ash pond is used as a landfill to
prevent the release of the ash into the atmosphere. While certainly
preferred to unrestricted release of the ash into the environment,
ash ponds themselves are significant environmental hazards.
[0025] The method produces calcium hydroxide through an aqueous
leaching-precipitation cycle aided by ammonia. The overall process
is described by the following two reactions:
2NH.sub.4Cl+H.sub.2O+CaSiO.sub.2.fwdarw.CaCl.sub.2+SiO.sub.2.dwnarw.+2H.-
sub.2O+2NH.sub.3.uparw. Reaction 1:
CaCl.sub.2+2NH.sub.3+2H.sub.2O.fwdarw.Ca(OH.sub.2).dwnarw.+2NH.sub.4Cl
Reaction 2:
[0026] In Reaction 1, calcium ions are extracted from
calcium-bearing minerals using an aqueous solution comprising a
water-soluble ammonium salt, preferably an ammonium halide salt,
and most preferably ammonium chloride, which is shown as the
exemplary ammonium salt in Reactions 1 and 2. Reaction 1 produces
calcium chloride solution (as shown in Reaction 1) or a calcium
salt comprising the anion from the water-soluble ammonium salt
used, along with leached mineral residue, and ammonia gas. In
Reaction 2, the calcium chloride solution and ammonia gas from the
first step are collected and reacted to yield calcium hydroxide,
which precipitates from the aqueous solution. The second reaction
utilizes the low and inverse solubility of calcium hydroxide to
induce precipitation at elevated temperature and mild
pressurization.
[0027] Regarding the inverse (or retrograde) solubility of calcium
hydroxide, the solubility of calcium hydroxide at 70.degree. C. is
about half of its value at 25.degree. C. This counter-intuitive
phenomenon arises because the dissolution of calcium hydroxide in
water is exothermic process and follows Le Chatelier's principle.
Thus, at lower temperatures, the elimination of the heat liberated
through the process of dissolution increases the equilibrium
constant of dissolution of calcium hydroxide.
[0028] Thus, it is preferred that Reaction 2 be conducted at a
pressure above atmospheric pressure and a temperature ranging from
roughly 25.degree. C. to the boiling point of the reaction solution
at the pressure chosen, and more preferably from about 70.degree.
C. to the boiling point of the reaction solution at the pressure
chosen. A preferred pressure range is from roughly 2 bar to about
10 bar.
[0029] The calcium hydroxide precipitate is then separated from the
reaction solution by conventional means. This can be done
continuously or batchwise, as is known in the industry.
[0030] After the calcium hydroxide precipitates are separated, the
ammonium chloride solution is recycled for use in the leaching step
shown in Reaction 1.
[0031] For a feedstock, the method can use crystalline, amorphous,
or hydrated phases of calcium silicates/aluminate/aluminosilicates.
Such materials are abundant in a wide range of industrial waste
streams, including crushed concrete, coal ashes, steel and iron
slags, etc.
[0032] The sustainable calcium hydroxide produced from this process
can replace limestone as the calcium source, offering a realistic
pathway to reducing the carbon footprint of the existing cement
industry by more than 50%. Furthermore, when combined with concrete
recycling and/or carbonation-based cementation technologies, it can
transform cement production into a carbon-negative industry. The
technology enables a pathway for direct capture of atmospheric
carbon as precipitated calcium carbonate, a valuable co-product,
and stable form of bound carbon.
[0033] On this score, the present method is a distinct improvement
over conventional methods to reduce the carbon emission of
cement/concrete production. Conventional methods, such as those
noted above, rely on blending cement with supplementary
cementitious materials such as coal fly ash or other fillers.
However, the typical replacement ratio is limited to 15-30%, and it
provides little benefit to cement producers.
[0034] Reactions 1 and 2 can be broken down further as shown in
FIG. 2. Reaction 1 can be parsed out as three separate reactions,
representing mineral dissolution and hydrolysis:
2CaO.SiO.sub.2+4H.sup.+.fwdarw.2Ca.sup.+2+SiO.sub.2.dwnarw.
1.a:
4NH.sub.4Cl.fwdarw.4NH.sub.4.sup.++4Cl.sup.- 1.b
4NH.sub.4.sup.+.fwdarw.4NH.sub.3.uparw.+4H.sup.+ 1.c:
The overall Reaction 1, excluding the water molecules, is thus:
CaO.SiO.sub.2+4NH.sub.4Cl.fwdarw.2Ca.sup.+2+2Ca.sup.+2+4Cl.sup.-+SiO.sub-
.2.dwnarw.+4NH.sub.3.uparw. 2
[0035] Similarly, Reaction 2 can be broken down as follows,
representing ammonia absorption and precipitation of calcium
hydroxide:
NH.sub.3(g)+H.sub.2ONH.sub.4.sup.++OH.sup.-(at increased pressure)
2.a:
Ca+.sup.2+2Cl--+2NH.sub.4.sup.++2OH.sup.-.fwdarw.Ca(OH.sub.2).dwnarw.+2N-
H.sub.4.sup.++2 Cl.sup.- 2.b:
[0036] FIG. 3 shows an exemplary schematic implementation of the
method disclosed and claimed herein. The various apparatus and
conduit shown in FIG. 3 is conventional and will not be described
in any detail. Starting at the upper left corner of FIG. 3, the
incoming powdered feedstock is fed into the process via a solid
sample feeder 10. The feedstock, along with ammonium chloride 12
(which can be virgin or recycled from the process) are fed into a
jacketed, temperature-controlled, stirred dissolution reactor 14.
Reaction 1 takes place within reactor 14. The reactants may be
reacted at room temperature up to the boiling point of solution
(roughly 100.degree. C.) and for a time sufficient to dissolve at
least a portion of any calcium compound present in the
feedstock.
[0037] The reaction solution is then transferred to
separator/settling tank 16, which is dimensioned and configured to
separate any precipitates from the reaction solution (principally
SiO.sub.2). The calcium-rich supernatant is optionally cooled (if
necessary) at process cooler 18 and pumped via pump 20 into reactor
22. Reactor 22 is operationally connected to a back-pressure
regulator 24. As noted in FIG. 3, the preferred pressure for the
reaction in reactor 22 is about 2 bar. Reaction 2 takes place in
reactor 22.
[0038] The contents of reactor 22 are then transferred to
separator/filtration unit 26 to recover the precipitated calcium
hydroxide.
[0039] Ammonia recovered in separator 26 is recycled back into the
process via condenser 28 and a separator 30. The separator 30 is
dimensioned and configured to separate ammonia from the process
water. The water is purged from the apparatus and send for
treatment. The ammonia is sent to an ammonia make-up unit 32. Unit
32 is dimensioned and configured to mix the recycled ammonia with
fresh ammonia and re-introduced into reactor 22 after optionally
being passed through mixer 34 and chiller 36.
[0040] Additionally, NH.sub.4Cl present in the effluent from
separator 26 is likewise recycled as shown at conduit 38 and used
to dissolve the incoming feedstock. Make-up NH.sub.4Cl may also be
added at 12.
[0041] The apparatus shown in FIG. 3 is exemplary only. Other
equally suitable means for implementing the method will be apparent
to chemical engineers of ordinary skill in the art.
* * * * *